I have this:

add_action( 'rest_api_init', function () {
  register_rest_route('my-project/v1/form', '/post', array(
    'methods' => 'POST',
    'callback' => 'post_form'
  ) );
});

I called it with this and the call gets done and serializedForm is not empty:

$(".my-project-submit").click(function(){
   var serializedForm = $('#my-project-form').serialize();
    $.post("/wp-json/my-project/v1/form/post/", serializedForm, function(data) {
        alert(data);
    });
});

I tried these:

function post_form($data) {

$data is null/empty.

function post_form($data) {
   $data = $request->get_params();

I don't know it $data is null, I just do not receive response ( alert(data) never reached).

    function post_form($data) {
       $data = $request->get_body();

I don't know it $data is null, I just do not receive response ( alert(data) never reached).

All test methods end with

    $response = new WP_REST_Response($data, 200);
    $response->set_headers([ 'Cache-Control' => 'must-revalidate, no-cache, no-store, private' ]);
    return $response;
}

I have this:

add_action( 'rest_api_init', function () {
  register_rest_route('my-project/v1/form', '/post', array(
    'methods' => 'POST',
    'callback' => 'post_form'
  ) );
});

I called it with this and the call gets done and serializedForm is not empty:

$(".my-project-submit").click(function(){
   var serializedForm = $('#my-project-form').serialize();
    $.post("/wp-json/my-project/v1/form/post/", serializedForm, function(data) {
        alert(data);
    });
});

I tried these:

function post_form($data) {

$data is null/empty.

function post_form($data) {
   $data = $request->get_params();

I don't know it $data is null, I just do not receive response ( alert(data) never reached).

    function post_form($data) {
       $data = $request->get_body();

I don't know it $data is null, I just do not receive response ( alert(data) never reached).

All test methods end with

    $response = new WP_REST_Response($data, 200);
    $response->set_headers([ 'Cache-Control' => 'must-revalidate, no-cache, no-store, private' ]);
    return $response;
}

• api
• endpoints

• 2 $request is undefined in your examples so it will never work, the parameter passed to the callback is the request object, but you've named yours $data for some reason, not $request – Tom J Nowell ♦ Commented Apr 12, 2019 at 15:28
• Indeed, you should write as answer ;-) – TTT Commented Apr 12, 2019 at 15:30
• Additionally, jQuery serialize generates a URL encoded string, it's not standard JS practice when using POST, and would require additional steps on the PHP end to deserialize – Tom J Nowell ♦ Commented Apr 12, 2019 at 15:30
• I would if i knew a full answer at hand, I know it's a part of the issue, but I don't know how to handle the usage of serialize in jQuery here. For reference, PHP should be giving you warning and notice messages in your error log for that code due to the use of an undefined variable, so check you've got your debugging setup right and PHP error logs are working – Tom J Nowell ♦ Commented Apr 12, 2019 at 15:31
• How should I do it instead of serialize? (I haven't setup debugging PHP debugging. Long story short, I come from C# where debugging mostly comes in 1 click. Deciding of environment/IDE for PHP developement has been a long headache-process which I'm not sure is becoming stable yet.) – TTT Commented Apr 12, 2019 at 15:41

1 Answer 1

Update your function post_form as

function post_form(WP_REST_Request $request)
{
    $data = $request->get_params();
    print_r($data);
}